The present invention relates to a pressure transmitter having a housing designed to reduce transmission of axial and radial clamping forces from the housing to a pressure transducer therein. Clamping forces are created by flanges urged against the housing, and can be uneven and hysteretic due to differential thermal expansion between the flanges, bolts and housing.
The need to reduce clamping forces distorting pressure transducers disposed within pressure transmitter housings has brought about improvements of pressure transmitter housings and methods for coupling fluid pressure to the pressure transducer. Flanges sealingly coupling fluid pressure to the pressure transducer typically apply large clamping forces to the pressure transmitter housing, known as preloading, which clamping forces can significantly distort the pressure transducer causing measurement errors.
Typically, large clamping forces are created by bolts urging the flanges toward the transmitter housing. These bolts are usually torqued to produce clamping forces in excess of 3000 pounds to preload the flange to the pressure transmitter housing, ensuring the flange remains sealingly coupled to an isolator diaphragm when coupling high fluid pressures.
Further, the transmitter housing, flanges and bolts typically comprise different materials having different thermal coefficients of expansion which create varying and unevenly distributed axial and radial components in clamping forces due to differential expansion and contraction of the flanges, housing and bolts over a temperature range.
Furthermore, slipping action between contiguous surfaces of the flange and the housing can generate radial components in clamping forces due to friction. The radial components are hysteretic versus temperature due to the flange slipping across the housing.
A pressure transmitter housing that substantially reduces transmission of large and unevenly distributed axial and radial clamping forces from the housing to a pressure transducer disposed therein is desirable. Further, a transmitter housing which reduces transmission of hysteretic radial clamping forces due to friction between contiguous surfaces of the housing and the flange due to temperature variations of the flange, housing and bolts is desirable.